This invention relates generally to nuclear reactors, and more particularly, to an instrument removal system to remove detector cables from their housing.
A reactor pressure vessel (RPV) of a boiling water reactor (BWR) typically has a generally cylindrical shape and is closed at both ends, e.g., by a bottom head and a removable top head. A core assembly is contained within the RPV and includes the core support plate, fuel assemblies, control rod blades and a top guide. A core shroud typically surrounds the core assembly and is supported by a shroud support structure. Particularly, the shroud has a generally cylindrical shape and surrounds both the core plate and the top guide. There is a space or annulus located between the cylindrical reactor pressure vessel and the cylindrically shaped shroud.
A plurality of detectors are utilized to monitor the reactor. Periodically detectors need to be removed for replacement. The detectors are typically positioned in a housing and are attached to cables for transmitting data. A known method of removing detectors includes the use of a bottom entry disposal system which utilizes a pinch wheel system to pull the detector cables from the housing. The detector cables are fed into a cutter for cutting into small two inch pieces for disposal. The detector cable pieces are fed into a disposal cask for transport and removal from the reactor. However, this method has some shortcomings, for example, pinch wheels can slip causing jammed detector cables and/or missed cuts. Also, cutters can jam and generate loose, irradiated chips. Further, disposal casks can fill unevenly which can make cask lids difficult to close.